disconnection times

disconnection times

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  1. B

    Correct OCPD for disconnection times.

    Simple question (or so I thought) What would be the Correct OCPD to achieve correct disconnect times for a 200amp sun-main with ze of 0.26 tncs. What are everybody’s thoughts??
  2. biaelectric

    Disconnection times on EPS circuits

    When there is a fault on an EPS circuit, how are we meeting the disconnecting times? Earth fault is easy - just use a 30mA B-type RCD, but for the overload, are MCB good enough? On a 3.6kW supply, the voltage will drop so quickly, will there be enough energy to trip conventional MCBs or do we...
  3. Y

    RCD disconnection times help!!

    Im suppling distribution circuits and want to use the largest possible RCD available to avoid nuisiance tripping (its for outdoor street furniture and its a TT system). The Ze is 160. The reg below says 1 second disconnection time but cant find anymore info in the regs about it. Closest I can...
  4. 0

    RCD disconnection times!

    Hi all, just a quick one regarding RCD disconnection times. So for non rcd protected circuits disconnection times of 0.4 / 5 seconds and 0.2 / 1 second for TN + TT final and distribution circuits. RCDs (fire / fault protection) usually 300ms at rcd for rated current. (differs when s type)...
  5. D

    0.4 seconds or 5 seconds

    Just a quick question. This might sound like a stupid question so apologises. I'm slightly confused with the regs 18th edition when it comes to disconnection times. So I was taught in college that in the 17th edition that when a circuit is less than 32A then the maximum permitted time is 0.4...
  6. B

    Disconnection times not met

    Three questions haha 1. 160A MCCB the max Zs for this particular switch is 0.25 ohms all tested and I’m getting 0.44 ohms its a 95 SWA outgoing which feeds another panel which has its own outgoing circuits would I be right and say that would be a code 2? As I can’t meet disconnection time on it...
  7. Mark Wright

    Disconnection Times Again! Fig 3A4

    Looking at Fig 3A4 Type B 60898 unless I'm getting it wrong once we In*5 our device there is no way of telling if our disconnection is 10s or 0.1s unless im missing something although this seems quite important??? as our Disconnection time needs to be at least 0.4 seconds and for doing our...
  8. D

    18th edition RCD max disconnection times!!

    Hi all. I am seeing different figures here all over the net, table3a (p363) states a 30ma RCD has a trip time of 300ms max. So at 5x is the maximum 60ms? I seem to recall 200ms and 40ms for a 30ma and these are the figures I am seeing over the net... Please I just want the correct figures for...
  9. C

    Maximum Disconnection Times

    What is the reasoning behind having a 0.8 disconnection time for up to 120 volts Uo, but it then jumps to 0.4 seconds as soon as you go over it? Wouldn't it be better 0.8 seconds for 150 volts Uo and under, 0.4 seconds 150 volts and over Uo?
  10. G

    Disconnection times, some clarification

    Evening, just revising for 18th update course and wondered if someone can just clarify something. (I might just be confusing myself, too long staring at the BBB) Reg 411.3.2.2 ii) does that also include luminaries? I understand 411.3.4 applies. Do notes 1 & 2 of 411.4.4 mean that the use of an...
  11. Pretty Mouth

    Short circuit disconnection times

    Could someone shed some light on the following please? 411.3.2.1 implies that the 5s / 0.4s disconnection times only apply to earth faults. I've not found anything else in the regs that suggests they apply to short circuits. 435.5.2 says faults should be disconnected before the fault current...
  12. S

    RCD disconnection times on 2018 forms

    Evening all, happy Friday! On the new forms there is only one column for RCD disconnection times. I understood you would just record the highest of the 5x readings but on looking around to confirm I found this article on Professional-Electrician: "The model forms in Appendix 6 have been...
  13. J

    Changes to the requirements on recording RCD disconnection times

    Hi everyone, long term visitor to the forum but first time posting a question... be gentle This question is with regards to the changes to the 18th edition certificates, which only require one disconnection time recorded. When recording the highest value taken when carry out RCD tests, Reg...
  14. gazdkw82

    Ax disconnection times 32A+

    I don't know why I've not noticed before but the disconnection time for final circuits greater than 32A is 5 secs on a TN earthing arrangement. Does that mean a shower has a disconnection time of 5 secs? Although this circuit would also fall under protection of an RCD?? Also, cooker circuits...
  15. R

    Disconnection times for finals

    Just received a completed test sheet from an installer on a TN system with the max permitted disconnection time column filled in for the lighting circuit and 20A heater circuit as 5secs, surely 0.4
  16. P

    Disconnection times help

    Hi all just a little bit of advice at the company i work has just had a condition report done and they have marked down excessive zs for a 63a type d breaker but they have put it at 0.4 disconnection time it is a permanent fixed compressor I thought this would have been 5 sec it also has a b.s...
  17. John Lundrigan

    I'm confused about Type C Breaker Disconnection Times

    Hi All, When I consult Table 41.3 for a Type C Breaker rated 16A I see s max Zs of 1.37 Ohms. However this value is defined for both a 0.4s AND 5s disconnection time. This is obviously correct so I am missing something. Fig 3A5 also shows the table 0.1s to 5s. Can anyone explain please...
  18. B

    Maximum disconnection times

    Hi does anyone know max disconnection times on tn-s system for: 16A radial 6A lights 32A distribution Cheers
  19. W

    Disconnection times

    Hello I understand why you need to find out the pfc to ensure breaking capacity is adequate. But I'm struggling to understand minimum fault current. Tncs e.g 230/0.35 =657 amps I think it's if the system has enough fault current to trip the breakers in time e.g a ring would be 3-5 times 32...
  20. Z

    Verifying SWA CPC suitability disconnection times / adiabatic equation

    As you may know looking at some of my posts I've been thrown back in the deep end recently – and don’t have much experience with complicated calculations. As this is the first time I've used SWA to go from the main supply to the primary CCU, and as I'm using the steel armour as my CPC, rather...

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